Project Summary/Abstract Kaposi's sarcoma-associated herpesvirus, also referred to as human herpesvirus-8, is the etiological agent of some of the most prevalent cancers in AIDS survivors. KSHV causes epidemic Kaposi's sarcoma, the most common AIDS defining illness. Additionally, KSHV causes primary effusion lymphoma and multicentric Castleman's disease. Integral to this widespread occurrence is the ability of KSHV to remain quiescent in host cells as a latent episome until the opportunity to proliferate within a compromised immune system. While much work has been done to understand the molecular basis of viral latency, studies of the three-dimensional organization of an infected nucleus have been lacking. How is the KSHV episome positioned in space to keep transcription quiescent during latency and active during lytic replication? Work on the closely related Epstein-Barr virus (EBV) discovered that EBV hides within human heterochromatin during latency. Upon reactivation, this network of interactions reorganizes toward human euchromatin. Contacts with the viral genome localize to OriP but do not require the viral protein EBNA1. Whether or not a similar strategy is employed by KSHV is the focus of this proposal. Specific Aim 1 will use chromatin conformation capture methods to determine the network of interactions between KSHV and the human genome during latency and reactivation. The role of LANA, the EBNA1 homolog in KSHV, in maintaining this network will also be examined. Specific Aim 2 will functionally test if tethering KSHV to specific chromatin compartments regulates transcription. Specific Aim 3 will ask if this organization, so far only observed in cell culture, also occurs in primary patient tissue. The sum of experiments will advance our knowledge of KSHV host-pathogen interactions in three-dimensional space.